Modular power transmission with self-energizing device

ABSTRACT

A power transmission comprises one or more sequential modules each including a modular portion of an enclosure for the complete transmission, a planetary gear set, a direct drive clutch, a self-energizing reduction brake and a hydraulic control system preferably adapted to substantially simultaneously condition the direct drive clutch and reduction brake for establishing either a direct or reduction drive mode for each module. The selfenergizing reduction brake is a friction device providing an automatically operable coupling between rotatable elements and includes a first friction component having a plurality of friction discs and a second split friction component having friction discs interleaved with those of the first component, split portions of the second friction component being axially movable by engagement with circumferentially spaced-apart, spiral teeth on the fixed housing for causing engagement and disengagement of the friction discs with control apparatus being operable to maintain the split portions of the second friction component in spaced-apart relation to assure disengagement of the reduction brake.

ttes tet [191 Nov. 4, 1975 MODULAR POWER TRANSMISSION WITHSELF-ENERGIZING DEVICE [75] Inventor: Charles H. Herr, Peoria, Ill.

[73] Assignee: Caterpillar Tractor Company,

Peoria, 111.

[22] Filed: Apr. 8, 1974 [21] Appl. No.: 459,109

[52] US. Cl. 74/751; 74/740; 74/767; 74/781 R; 192/54 [51] Int. Cl. F16H3/54 [58] Field of Search 74/781 R, 751, 767, 731, 74/740; 192/12 C [56]References Cited UNITED STATES PATENTS 2,136,971 11/1938 Fleischel74/752 A 2,254,335 9/1941 Vincent 74/781 R X 2,349,410 5/1944deNormanville 74/781 R 2,507,050 5/1950 Roberts 74/781 R 3,146,6379/1964 Whateley et al. 74/781 R 3,182,528 5/1965 Lamburn 74/781 R X3,290,962 12/1966 McCann et al. 74/760 3,303,726 2/1967 Christensen74/751 3,487,726 l/1970 Burnett 74/781 R Primary ExaminerSamuel ScottAssistant Examiner-John O. Reep Attorney, Agent, or Firm-Phillips,Moore, Weissenberger Lempio & Strabala [57] ABSTRACT A powertransmission comprises one or more sequential modules each including amodular portion of an enclosure for the complete transmission, aplanetary gear set, a direct drive clutch, a self-energizing reductionbrake and a hydraulic control system preferably adapted to substantiallysimultaneously condition the direct drive clutch and reduction brake forestablishing either a direct or reduction drive mode for each module.The self-energizing reduction brake is a friction device providing anautomatically operable coupling between rotatable elements and includesa first friction component having a plurality of friction discs and asecond split friction component having friction discs interleaved withthose of the first component, split portions of the second frictioncomponent being axially movable by engagement with circumferentiallyspaced-apart, spiral teeth on the fixed housing for causing engagementand disengagement of the friction discs with control apparatus beingoperable to maintain the split portions of the second friction componentin spaced-apart relation to assure disengagement of the reduction brake.

13 Claims, 17 Drawing Figures I33 I09 I28 II 4 II p 23 58 56 urns I22|2| 57 US. Patent Nov. 4, 1975 Sheet 2 of 9 3,916,72

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M2} I 14 I34 159 I47 57 I57 I I7 US. Patent Nov. 4, 1975 Sheet 7 of93,916,729

H8ll6 I2! l26 n2 H9 H7 I23 U.S. Patent Nov. 4, 1975 Sheet 8 of93,916,729

US. Patent Nov. 4, 1975 Sheet 9 of9 3,916,729

I47 57 I57 4| I39 I22 llA MODULAR POWER TRANSMISSION WITHSELF-ENERGIZING DEVICE BACKGROUND OF THE INVENTION The present inventionrelates to a power transmission including one or more speed ratiomodules each capable of operating in either a direct or reduction drivemode. The invention preferably contemplates the power transmission ashaving a modular construction wherein each speed ratio module includes aportion of the housing for the entire power transmission. The inventionalso particularly contemplates a unique friction device which isself-energizing to provide a selective coupling between relativelyrotatable elements such as may be found in a power transmission of thetype referred to above.

In the past, power transmissions have usually been designed incontemplation of a particular application. Accordingly, for a relativelybroad line of vehicles of machines there may arise a need for acorrespondingly wide variety of power transmissions. Generally, the needfor efficient operation of a power. transmission within each of thevehicles or machines has dictated the production of a generally uniquepower transmission for each application. This in turn has led to theneed for manufacturing and stocking a large variety of parts for thevarious power transmissions.

It is also noted that power transmissions of the type contemplated bythe present invention have generally required at least a direct driveclutch or brake and a reduction drive clutch or brake in combinationwith each planetary gear set in the power train. Complex mechanisms arecommonly required for synchronizing operation of the various gear trainsof the power transmission and particularly for precisely timingoperation of the large number of clutches or brakes associated with thevarious speed ratio gear sets within the power transmission. The needfor such mechanically complex control systems has also resulted in asubstantial expense for manufacture and maintenance of the powertransmission.

It has also been known in the past to employ selfenergizing frictiondevices within such power transmissions for selectively couplingrelatively rotatable shafts or elements. Cam and roller or sprague-typeoverrunning devices, for example, are often employed for this purpose inpower transmissions. However, such devices have certain limitations. Forexample, they generally are self-energizing only in one direction ofrelative rotation. Thus, they may be employed to transmit drive torquefrom an input shaft to an output shaft while not being capable oftransmitting coast torque from the output shaft to the input shaft.

A one-way, self-energizing friction device of the type referred toimmediately above may be seen in US. Pat. No. 2,939,343. Additionalexamples of overrunning devices which are self-actuating in only onedirection of relative rotation may be seen in US. Pat. Nos. 3,567,000and 3,730,314, assigned to the Assignee of the present invention.

It is particularly contemplated within the present invention to providea power transmission speed ratio module which may be assembled to form avariety of power transmissions suited for different machine or vehicleapplications. Such power transmissions normally include an input modulesuch as a torque converter or slipping clutch followed by one or morespeed ratio modules according to the present invention and a suitableoutput module. The present invention even more particularly contemplatesone-of such modules to form automatically controlled power shifttransmissions adapted for either on-highway or off-highway vehicles.With such applications, the power shift transmissions serve to extendthe working speed and torque range of any selected prime mover such as apiston engine, rotary combustion engine, gas turbine or electric motor,for example.

The primary purpose of the present module concept for powertransmissions is the reduction of manufacturing and service coats whilemaintaining reliability of operation. The use of identical speed ratiomodules or a selected series of such modules having different reductionratios would reduce the number of parts required in power transmissionsfor a variety of applications. This in turn would permit volumeproduction of the transmission parts and the use of automated productionfacilities.

As noted above, the present invention also particularly contemplatesnumerous specific features which may be employed within a modular powertransmission of the type discussed above as well as in otherapplications. Such specific features include, but are not limited to,the self-energizing clutch or friction device referred to above as wellas a common control assembly employed to condition both the direct driveclutch and the reduction drive clutch to selectively establish differentspeed ratios within each module.

The term friction device is employed below and particularly within theclaims with the intention of encompassing both clutches and brakes, forexample. The particular device as illustrated in the drawings outlinedbelow and described within the specification may arguably be considereda brake, since one portion of the device is fixed against rotation. thefriction device serves to condition the transmission or a modularportion thereof for the transmission of torque in different modesdepending upon operating conditions and associated control apparatus.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide apparatus for overcoming one or more of theproblems summarized above as well as for achieving one or more of thenoted advantages.

It is a particular object of the invention to provide a modularconstruction for power transmissions in order to facilitate theconstruction or assembly or power transmissions adapted to a variety ofapplications, for example.

It is a further object of the invention to provide a speed ratio modulefor a power transmission wherein a direct drive clutch and a reductionbrake are both operated in common by suitable control apparatus in orderto simplify construction, operation and maintenance of the transmission.

It is also a particular object of the invention to provide a modularpower transmission wherein each speed ratio module includes a housingforming a portion of an enclosure for the entire power transmission.

It is another particular object of the invention to provide aself-energizing friction device for providing a selectively operablecoupling between relatively rotatable elements.

The self-energizing friction device may be employed within powertransmissions of the type referred to above as well as in otherapplications. The invention particularly contemplates use of theself-energizing friction device as a reduction brake which may beconditioned to automatically transmit drive torque from an input memberto an output member as well as for transmitting coast torque from theoutput member to the input member. This capability of the frictiondevice may also be employed in other applications to achieve a selectivecoupling between rotatable elements upon the initiation of relativerotation therebetween in either direction.

Additional objects and advantages of the invention are made apparent inthe following description having reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation,with parts in section, of a power transmission constructed according tothe present invention and having three speed ratio modules providingfour speed ratios.

FIG. 2 is a view similar to FIG. 1 except that its power transmissionhas four speed ratio modules providing five speed ratios.

FIG. 3 is a tabular representation denoting those clutches within thepower transmission in FIG. 2 which are engaged to provide each speed aswell as the resulting gear ratio.

FIG. 3a is also a tabular representation denoting the relative torquedeveloped in each of the clutches of the power transmission of FIG. 2for each of the five speed ratios assuming input torque of 1.00.

FIG. 4 is another schematic representation of a power transmissionsimilar to that of FIG. 2 while including a different directional modulefor establishing forward and reverse operation.

FIG. 5 is a vertically sectioned view of a directional module andsequentially adjacent speed ratio module from a power transmission suchas that also illustrated in FIG. 4.

FIG. 6 is side view of a power transmission of the type also illustratedin FIG. 1, with parts broken away to illustrate modular construction ofthe transmission according to the present invention.

FIG. 7 is an enlarged fragmentary view, with parts in section, of areduction brake incorporated within the speed ratio module illustratedtoward the right of FIG. 5.

FIG. 7A is a fragmentary view taken along section line AA of FIG. 7 tobetter illustrate the angular arrangement of selected portions in thebrake.

FIG. 7B is an isometric view of a spiral spring associated with thebrake of FIGS. 5 and 7.

FIGS. 8 and 8A are similar to FIGS. 7 and 7A, except that theyillustrate a different operating condition of the brake.

FIGS. 9 and 9A are also similar to FIGS. 7 and 7A while illustrating yetanother operating condition of the brake.

FIG. 10 is a side view in elevation, with parts in section, of afragmentary portion of one speed ratio module in a power transmission ofthe type illustrated in FIGS. 1 or 2, as well as the directional moduleshown at the right end of FIGS. 1 and 2. I

FIG. 11 is a view similar to FIG. 7 while illustrating a selectedoperating condition of an additional embodiment of the reduction driveclutch within a speed ratio module associated with the directionalmodule of FIG. 10.

FIG. 11A is a view taken along section line AA of FIG. 11 to againillustrate the angular relation of selected portions in the reductionbrake.

Referring now to the drawings, FIGS. 1 and 2 schematically representpower trains of the type contemplated by the present invention. Each ofthese power trains includes an input module 11 for receiving power froma prime mover such as an engine. The input module 11 preferablycomprises a torque converter 12 having its impeller element 13 coupledwith the engine by means of an input element or rotatable housingindicated at 14. The turbine element 16 is conventionally associatedwith the impeller element 13 and a stator element 17 while also beingcoupled for rotation with an output shaft 18 of the torque convertermodule. A con ventional lock-up clutch 19 is selectively operable tomechanically couple the input element 14 with the output shaft 18 inorder to effectively bypass the torque converter.

The input module 11 is sequentially coupled with one or more speed ratiomodules preferably constructed in accordance with the present invention.For example, the power transmission of FIG. 1 includes three speed ratiomodules providing a selection of four speed ratios within the powertransmission. The power transmission of FIG. 2 includes four speed ratiomodules indicated respectively at 21, 22, 23, and 24, the last speedratio module for each of the power trains being coupled with an outputmodule 26 which has a directional function for driving an output shaft27 in either forward or reverse.

Each of the speed ratio modules includes a planetary gear set 28 havinga sun gear 29 and a ring gear 31. Planetary gears 32 are mounted upon arotatable carrier element indicated at 33 while being in meshingengagement with both the sun gear 29 and the ring gear 31.

The ring gear 31 of the first speed ratio module 21 is coupled with theoutput shaft 18 of the torque converter module. The carrier element 33delivers output torque from the speed ratio module 21 and is accordinglycoupled with the ring gear 31 of the next adjacent speed ratio module22. Similarly, the carrier elements of the speed ratio modules 22 and 23are coupled respectively with the ring gears 31 of the speed ratiomodules 23 and 24 respectively. The carrier elements 33 for the finalspeed ratio module 24 is coupled with a shaft 34 which also acts as aninput for the directional module 26.

The speed ratio module 21 includes a direct drive clutch 36 which isengageable to couple the respective ring gear 31 for rotation togetherwith the sun gear 29 of the same planetary gear set. The successivespeed ratio modules 22, 23, and 24 have similar direct drive clutchesindicated respectively at 37, 38 and 39. The direct drive clutchesfunction upon engagement to provide a unitary drive ratio across theirrespective speed ratio modules.

Each speed ratio module also has a reduction brake indicatedrespectively for the four speed ratio modules of FIG. 2 at 41, 42, 43and 44. Each reduction brake is selectively operable in a mannerdescribed in greater detail below to lock the respective sun gear 29against rotation whereupon the planetary gears 32 are caused to rotatebetween the driven ring gear 31 and the fixed sun gear 29 to causerotation of the associated carrier at reduced speed and increasedtorque.

The output shaft 34 from the final speed ratio module 24 is coupled withthe sun gear 46 of a planetary gear set 47 in the directional module 26.The planetary gear set 47 also includes a ring gear 48 and a pluralityof planetary gears 49 intermeshed between the sun gear 46 and ring gear48 while being mounted upon a carrier element 51 which is fixed againstrotation.

Directional transmission from the planetary gear set 47 to the outputshaft 27 is established by sliding collar gears 52 and 53 which arecoupled respectively with the sun gear and the ring gear. The collargears 52 and 53 are respectively engageable with gears54 or 56 arrangedupon the output shaft 27 to drive the output shaft 27 in forward orreverse directions respectively.

The module 26 is a highly efficient directional unit while requiringsubstantially complete termination of movement in its planetary gear set47 before shifting the collar gears 52 and 53 for changing the directionof rotation of the output shaft 27. Accordingly, the directional module26 is particularly contemplated for use in on-highway vehicles whileanother directional module is described below for use in combinationwith the same type of speed ratio module in applications requiring morerapid and more frequent directional changes.

The particular arrangement of the speed ratio modules is selected toprovide an effective gradient in speed ratios for the entire powertransmission. For example, in the first speed of the power transmissionin FIG. 2, each module has its reduction brake engaged with reactiontorque being distributed among the four reduction drive brakes 4l44.Assuming a 1.5:1 reduction ratio, the overall reduction across the fourspeed ratio modules would be 1.5 or 5.063. Since reaction torque is thedifference between output torque and input torque, and a module with1.5:1 reduction and input torque taken as unity, output torque would be1.5 and reaction torque would be 0.5. Accordingly, in the powertransmission of FIG. 2, assuming an input torque to the first speedratio module 21 of 1.0, reaction torque on the brake 41 would be 0.5.Reaction torque on the brake 42 would be 0.75. Similarly, reactiontorque would be 1.25 on the reduction clutch 43 and 1.688 on thereduction brake 44. Accordingly, even with maximum reduction across thepower transmission, the reaction torque is relatively limited for anygiven brake.

Upon engagement of the respective direct drive clutches, the sun gearsand ring gears are locked together and accordingly cause the carrier tobe rotated at the same speed so that torque input equals torque outputacross each of the speed ratio modules so engaged. This relationship maybe further seen from a review of FIG. 3 which lists the gear ratioestablished within each operating speed ratio and indicates the engagedcondition of the clutches. FIG. 3A lists the corresponding torqueresulting upon each clutch within the various speed ratios. The twocharts taken together, indicate a relatively uniform gradation betweengear ratios while also indicating relatively minimum and uniform torqueapplied to the various clutches and brakes. This arrangement for thespeed ratio modules is preferred within the present invention where thespeed ratio modules are constructed with modular portions for assemblyinto the complete power transmission.

As may be best seen in FIGS. 5 and 6, each of the speed ratios modulesis formed with a separate fixed housing 57 of similar construction sothat the housing portions of the sequentially arranged speed ratio modules combine to form an enclosure for the assembled power transmission.The housing portions 57 are secured together by elongated bolts 58 (seeFIG. 5). The joints between the housing portions 57 are conventionallysealed, preferably by means of a liquid gasket material (not shown).

Additional features include a common center shaft indicated at 59 inFIG. 5 for supporting the planetary gear sets of the sequentiallyarranged speed ratio modules. In addition, a lower portion of eachmodular housing 57 includes a sump passage 61 extending thereacross.When the housing portions are assembled together, a common sump isformed for the assembled power transmission as best seen in FIG. 6. Thisfeature enables the housing portions 57 to be assembled into a finishedenclosure since the common sump eliminates the need for a conventionaloil plan arrangement extending beneath the sequentially arrangedmodules.

FIG. 4 is a schematic representation of a power transmission generallysimilar to that of FIG. 2 in that it includes four similar speed ratiomodules 21-24. However, in place of the directional output module 26 ofFIG. 2, a directional module 62 is inserted between the torque convertermodule 11 and the first speed ratio module 21. The directional module 62also has a planetary gear set 63 while including frictional clutches 64and 66 which are respectively engaged to provide a forward or reversedrive connection between the torque converter module 11 and the firstspeed ratio module 21. A directional module of the type indicated at 62facilitates faster or more frequent directional changes and accordinglyis more desirable for use in offhighway vehicles. The clutches in thepower transmission of FIG. 4 are engaged in generally the same manner asthose of FIG. 2with the gear ratios and resultant torques for thevarious clutches also being similar to those in the tables of FIGS. 3and 3A.

The manner of operation for the directional modules 26 and 62 isdescribed in greater detail below along with details of construction andoperation for the speed ratio modules 21-24. As noted above, theconstruction and manner of operation for the reduction brake 41-44 isbelieved to be a particularly novel feature of the present invention aswell as the common actuating arrangement for the direct drive clutch andreduction brake of each speed ratio module.

Referring now to FIG. 5 as well as FIG. 4, the directional module 62includes a stationary housing portion 67 of similar construction as thehousing portions 57 for the various speed ratio modules. Accordingly,the directional module 62 may be readily assembled in sequentialrelation between the converter module 11 while being secured in place bythe bolts 58.

The converter module 11 is partially illustrated in FIG. 5 together withits output shaft 18. The common center shaft 59 may be supported at itsleftward end, as viewed in FIG. 5, upon the input shaft 18 by means of acoupling generally indicated at 68. The center shaft 59 provides supportfor a plurality of bearing supports 69 pressed in shaft 76 in module 62and shafts 107 in modules 2124.

The center shaft 59 also includes an axial passage 71 in communicationwith respective outlet passages 72 for communicating lubricating oilfrom a source (not shown) to each of the modules illustrated in FIG. andFIG. 2. The right end of the common center shaft 59 is similarlysupported upon an output shaft by means of a bearing or coupling similarto that indicated at 68 in FIG. 5, (also see FIG. 10).

The planetary gear set 63 of the directional module 62 has a sun gear 73which is coupled with the input shaft 18 by means of splines 74. Thedirectional module 62 also includes an output sleeve 76 supported forrotation upon the center shaft 59 by means of the bearing supports 69.The output sleeve 76 provides a coupling with the adjacent module 21 ina manner described in greater detail below. Respective engagement of thefriction clutches 64 and 66 causes rotation of the output sleeve 76 sothat the speed ratio module 21 and successive portions of the powertransmission are operated in a forward or reverse directionrespectively.

The planetary gear set 63 of the directional module 62 also includes aring gear '77 with a plurality of planetary gears 78 arranged in meshingengagement between the ring gear 77 and the sun gear 73. The planetarygears 78 are supported by a carrier 79.

The forward friction clutch 64 includes interleaved friction discsengagable with each other through axial movement of a piston 82 tocouple a gear member 83 together with a rotatable housing member 84. Thegear member 83 is also secured to the sun gear 73 by splines 86 whilethe housing member 84 is secured to the output sleeve 76 by means ofsplines 87. Accordingly, engagement of the forward clutch 64 serves tolock the sun gear 73 for rotation with the output sleeve '76 with theoutput sleeve 76 rotating in the same direction as the input shaft 18.

The reverse clutch 66 also includes interleaved friction discs 88 whichare engagable to lock the carrier member 79 to a portion 89 of thedirectional module housing 67 in order to secure the carrier memberagainst rotation. With the reverse clutch or brake 88 engaged, the ringgear 77 is driven in the opposite direction from the sun gear 73 throughthe planetary gear 78. Since the housing member 84 is secured to thering gear 77 by means of a spline coupling 91 and an annular coupler 92,the output sleeve 76 is rotated in the opposite direction so that theadjacent speed ratio module 21 and successive portions of the powertransmission are driven in reverse. The forward clutch 64 is engaged byhydraulic fluid under pressure introduced through passages 93 and 94into an annular cavity 95 adjacent the piston 82. Similarly, the reversebrake is actuated or engaged by hydraulic fluid under pressure beingcommunicated against a piston 96 through passages 97 and 98. Movement ofthe piston 96 is transmitted to the reverse brake 88 by means ofa sleeve99 and a pressure plate 101. Hydraulic fluid under pressure may beselectively introduced into the passages 93 and 97 for actuating theforward and reverse clutches 64 and 66 by conventional control means(not shown).

As noted above, the speed ratio modules 21-24 are of similarconstruction. Accordingly, the following description which isparticularly directed toward the speed ratio module 21 also applies tothe other speed ratio modules 22-24. However, it is to be noted thatwhere a large variety of power transmissions are required for differentapplications, a family of speed ratio modules may be designed,particularly for the purpose of providing a variety of reduction ratios.Accordingly,

if such a family of speed ratio modules were available, a single powertransmission might be assembled in modular fashion from speed ratiounits having different reduction ratios. This might permit a successionof stepped gear ratios better suited to a particular application.

Referring again to FIG. 5, drive torque from the output sleeve 76 of thedirectional module 62 is delivered to the first speed ratio module 21 byan intput gear 102. The gear is respectively coupled with the outputsleeve 76 and the ring gear 31 by spline connections indicatedrespectively at 103 and 104. The carrier element 33 of the speed ratiomodule 21 is coupled by means of a spline connection 106 with an outputsleeve 107 which is of substantially similar construction as the outputsleeve 76 in the directional module 62. The output sleeve 107 is alsomounted upon the common center shaft 59 by means of the bearing supports69 and is coupled by means of a spline connection 108 with an input gear109 for the next adjacent speed ratio module 22. The input gear 109 ofcourse corresponds with the input gear 102 for the speed ratio module21. The successive portions of the speed ratio module 22 also conform toportions described herein for the speed ratio module 21.

To provide a direct drive coupling across the speed ratio module 21, thedirect drive clutch 36 is engaged to effectively couple the ring gear 31for rotation together with the sun gear 29. The carrier 33 is driven atthe same rotating speed by the planetary gear 32 to provide a directdrive coupling between the input gear 102 and the output sleeve 107.

The ring gear 31 provides a first friction component for the directdrive clutch 36 and carries a plurality of friction discs 111. A commonclutch hub 112 is coupled with the sun gear 29 by means of a splineconnection 113 and extends outwardly to annularly surround the ring gear31. The clutch hub 112 forms a second friction component for the directdrive clutch 36 and also carries a plurality of friction discs 14 whichare arranged in interleaved relation with the friction discs 111.

The reduction brake 41 is particularly contemplated as beingself-energizing to provide a selective coupling between the sun gear 29by means of the common clutch hub 112 with the fixed housing 57 for thespeed ratio module 21. Construction details for the reduction brake 41are set forth in substantially greater detail below with reference toFIG. 7.

It is important at this point to note that the common clutch hub 112also acts as one friction component for the reduction brake 41.Accordingly, the common clutch hub 112 carries another set of frictiondiscs 1 16. A second split friction component for the reduction brake 41is formed by a clutch brake 117 carrying a plurality of friction discs118 arranged in interleaved relation with the friction discs 116. Thesecond friction component of the reduction brake 41 also includes areaction disc 119 which is secured for rotation with the brake drum 117while being axially movable in relation to the brake drum 117. Axialmovement between the drum 117 and reaction disc 119 serves to regulateengagement and disengagement between the interleaved friction discs 116and 118. The reaction disc 119 also includes a plurality of axiallyextending slots 121 formed about its periphery. The brake drum 117 has aplurality of axially extending fingers 122 which penetrate the slots 121for the purpose of permitting positive disengagement of the reductionbrake 41.

The manner in which the reduction brake 41 responds to relative rotationbetween the sun gear 29 and the fixed housing 57 to cause engagement ordisengagement between the interleaved friction discs 116 and 118 isdescribed below with reference also to FIG. 7. However, the componentsdescribed above are sufficient to permit an understanding of a commoncontrol apparatus for simultaneously conditioning the direct driveclutch 36 and the reduction brake 41 to establish a preferred manner oftorque transmission through the speed ratio module 21.

The brake drum 117 may be maintained in a position shifted axially awayfrom the reaction discs 119 by means of a blocker piston 123 slidablyarranged in axial alignment with the fingers 122. Leftward movement ofthe blocker piston 123 is limited by a retaining ring 124 with thepiston 123 being movable in response to fluid under pressure receivedthrough a communicating passage 126 from a common fluid passage 127.

Another actuating piston 128 for the direct drive clutch is slidablyarranged within a cavity 129 formed by the common clutch hub 112. Thepiston 128 interacts with a finger spring 131 having an extendingportion 132 arranged to selectively provide clamping force for theinterleaved friction discs 111 and 114 of the direct drive clutch 36.

Hydraulic fluid for shifting the piston 128 leftwardly against thefinger spring 131 is communicated from the common fluid passage 127through a restrictive orifice 133. As fluid pressure is introduced intothe common passage 127, it immediately shifts the blocker piston 123leftwardly to assure axial separation between the brake drum 117 and thereaction disc 119. Almost simultaneously, fluid from the passage 127acts against the piston 128 to shift both the piston 128 and fingerspring 131 leftwardly to clamp the interleaved friction discs 111 and114 together and establish an engaged condition for the direct driveclutch 36. However, the restrictive effect of the orifice 133 and thehigh-rate spring effect of the finger spring 131 serve to modulateengagement of the direct drive clutch 36 and thus facilitate shifting ofthe speed ratio module 121 into a direct drive condition.

Through this arrangement, the provision of control signals for operatingboth the direct drive clutch 36 and the reduction brake 41 isparticularly simplified. For example, the speed ratio module 21 may beupshfited into a direct drive condition by a single fluid pressuresignal introduced into the common fluid passage 127. Similarly, thespeed ratio module may be downshifted from a direct drive condition intoa condition where the reduction brake 41 functions automatically toprovide reduction drive by simply evacuating fluid pressure from thecommon passage 127. The provision of the common clutch hub 112 as afriction component in each of the direct clutch 36 and the reductionbrake 41 obviates or reduces the need for complex apparatus to assureproper timing in the control system for these two clutches, while alsoassuring continuous torque transmission across each speed ratio moduleduring speed ratio shifts.

The reduction brake 41 is self-energizing in either direction when therespective speed ratio module is in a reduction drive mode. The brake 41may also be conditioned by the blocker piston 112 to act as anoverrunning clutch when the respective speed ratio module is in a directdrive mode.

The modular transmission disclosed above is a preferred or exemplaryenvironment for the reduction brake. However, it is believed obviousthat a friction device including features of the brake 41 can be used toadvantage in many applications, primarily as a selective couplingbetween rotatable elements.

As noted above, the common clutch hub 112 forms one component of thereduction brake 41 while being secured for rotation with the sun gear29. Both the brake drum 117 and the reaction disc 119, comprising theother friction component of the clutch, are associated with the fixedhousing 57 in a manner which may be better seen by having reference alsoto FIG. 7. Accordingly, within the speed ratio module, the sun gear 29and the housing 57 are relatively rotatable elements between which thereduction brake of the present invention serves as a selective coupling.

Referring now to FIG. 7 as well as FIG. 5, a plurality of spaced aparthelical teeth 134 are formed upon an internal surface 136 of the fixedhousing 57. The circumferentially spaced apart relation of the teeth 134may be better seen in FIG. 7A. The brake drum 117 also has a pluralityof teeth 137, each of the teeth 137 projecting radially outwardly into aspace 138 between a pair of the helical teeth 134. The reaction disc 119is similarly formed with a plurality of circumferentially spaced apartteeth 139, each of the teeth 139 also projecting radially outwardly intoone of the spaces 138.

It is noted again that the brake drum 117 and the reaction disc 119 aresecured together for rotation while being axially movable relative toeach other. Accordingly, the teeth 137 and 139 are also necessarilyfixed together for rotation while being axially movable with relation toeach other and within the spaces 138 between the helical teeth 134.

It may also be seen from FIG. 7A that each of the spaces 138 issubstantially larger than the width of the teeth 137 and 139. This is toinsure that only one of each pair of teeth 137 and 139 is in engagementwith one of the two adjacent helical teeth 134 depending upon thecircumferential positioning of the teeth 137 and 139 as determined bythe rotation of the brake drum 117 and reaction disc 119. The teeth 137and 139 also have a helical configuration preferably to facilitateengagement with the helical teeth 134.

The interleaved friction discs 114 and 116 have a tendency to be drawntogether into engaged condition by surrounding hydraulic fluid uponrelative rotation being initiated between the clutch hub 112 and thehousing 57. However, the present invention also preferably contemplatesresilient means for urging the brake drum 117 and reaction disc 119axially toward each other to initiate engagement of the reduction driveclutch 141. That function could be accomplished by any resilient means,for example, hydraulic pressure or a plurality of coil springs. However,the resilient means is preferably embodied in a split annular ringhaving an axially arranged spiral configuration. As may also be seen inFIG. 7B, the spring 141 is formed as a single coil having a selecteduniform dimension indicated at 142 relative to the axis of the brakedrum 117. The spring 141, constructed in the above manner, serves thedual functions of urging the brake drum 117 rightwardly toward thereaction disc 119 while also serving as a stop to positively limit axialtravel of the brake drum 117 away from the reaction disc or in aleftward direction as viewed in FIG. 7, while under compression. As maybe seen in FIG. 7, the spring 141 is arranged for axial interactionbetween the brake drum 117 and a spaced apart surface 143 formed by oneof the housing portions 57.

The spring 141 has a number of lugs or projections 146 which serve toradially locate the spring during its interaction with the brake drum117. The housing portion 57 also forms a stepped surface 144 whichlimits rightward movement of the reaction disc 119 while allowing thefingers 122 of the brake drum to move freely toward the right forengagement of the friction surface members 116 and 118.

The brake drum 117 and reaction disc 119 tends to move axially towardseach other upon relative rotation being initiated between the clutch hub112 and the housing 57. This axial movement is initiated by engagementof either teeth 137 or 139 with the spiral teeth 134 depending upon therelative direction of rotation. It will also be apparent from a reviewof FIG. 7 that the blocker piston 123 can maintain the brake drum 117 ina leftwardly shifted position to prevent engagement of the reductiondrive clutch 141. In this connection, it may also be seen that thereaction disc 119 has a radially inwardly projecting collar 148 to limitits leftward movement shown in FIG. 11.

The novel configuration and mode of operation for the friction device orreduction brake 41 is made even more apparent by the followingdescription of its operation in conjunction with the speed ratio module21. The position or condition of the reduction brake 41 as illustratedin FIGS. 7 and 7A corresponds to a reduction drive mode for the speedratio module where both of the pistons 123 and 128 (see FIG. are fullyshifted to the right. Accordingly, the direct drive clutch 36 isdisengaged and a reduction drive coupling is provided by theself-energizing reduction brake 41. Assuming that a substantial load isplaced upon the output of the entire power transmission and accordinglyupon the output shaft 107 for the speed module 21, torque within thereduction clutch 41 is opposite engine torque and the teeth 139 of thereaction disc 119 are in engagement with the spiral teeth 134. As may beseen in FIG. 7A, the reaction disc 119 is thus shifted leftwardly whilethe brake drum 117 is being shifted rightwardly by the spring 141.Accordingly, the interleaved friction discs 1 16 and 118 are engaged tosecure the clutch hub 112 and the sun gear 29 against rotation. Reactiontorque for the brake 41 is applied to the housing portion 57.

Transition from the reduction drive mode of the speed ratio module intoa direct drive mode is accomplished by hydraulic pressure beingintroduced into the common fluid passage 127 (see FIG. 5). That pressureurges the reaction piston 123 leftwardly and, after a brief delay causedby the orifice 133, also acts upon the piston 128 and shifts itleftwardly as well. As the direct clutch 36 commences engagement, itstorque is applied in engine direction from the input gear 102 and ringgear 31 to the clutch hub 112 which is still being held against rotationby the reduction brake 41, wherein torque is opposite to engine rotationas noted above. As the direct clutch torque increases, itcorrespondingly causes a decrease in torque across the reduction brake41. When torque within the direct clutch 36 exceeds torque upon thereduction brake 41, the reduction brake begins to rotate in enginedirection. This eliminates contact of teeth 139 and establishes contactbetween teeth 137 and teeth 134. This contact urges brake 41 rightwardlyuntil fingers 122 of drum 117 engage blocker piston 123. With apredetermined clearance between the fingers 122 and slots 121 and in theproper relation, reaction disc 119 can continue to move rightwardly,until the friction surfaces of clutch 41 is eliminated, releasing clutchhub 112 from housing portion 57.

The reduction brake 41 is thus placed in an overrunning condition withthe speed ratio module being in its direct drive mode as shown in FIG. 9and FIG. 9A.

The transition from the direct drive mode of the speed ratio module toits reduction drive mode is accomplished simply by relieving fluidpressure from the common fluid passage 127. As the pistons 123 and 128again shift toward the right, the direct drive clutch 36 begins to slip,allowing the sun gear 29 and common clutch hub 112 to diminish speed orcommence turning backward relative to the direction of engine rotation.As those components stop rotation relative to the housing 57 andcommence to actually turn in the opposite direction, the teeth 139 onthe clutch drum contact the spiral teeth 134 (as may be best seen inFIG. 7A), thus initiating engagement of the reduction brake 41.

As noted above, an important function of the reduction brake 46 is alsoto transmit coast torque. Coast torque as used herein is intended todefine a situation where a load at the output of the power transmissionis actually driving a prime mover coupled to the input shaft of thetransmission. This condition, of course, commonly occurs in vehiclestraveling downhill. Under such conditions, an upshift into a directdrive condition may be forced if the vehicle is not braked and dependingupon the control selected for the various components of the powertransmission. However, with the speed ratio module remaining in itsreduction drive mode, relation of the reduction brake parts isillustrated in FIG. 8A. The reaction disc 1 19 is shifted rightwardlyagainst the stop 144 and the teeth 137 on the clutch drum are engagedwith the spiral teeth 134 to provide clamping force for the reductionbrake 41.

Once an upshift occurs, the blocker piston 123 and direct clutch piston128 are necessarily pressurized. The blocker piston 123 must thenovercome the axial force developed by the clutch assembly in order tomove the clutch drum 117 to the left and disengage the reduction brake46. The direct drive piston 128 is simultaneously moving toward theleft, after a slight modulation lag caused by the orifice 133 (see FIG.5) to initiate full engagement of the drive clutch 36. Engagement of thedirect drive clutch 36 is further modulated by the high rate spring 131.

A modification of the reduction brake is illustrated in FIG. 11 and ispreferably contemplated for use in at least one of the speed ratiomodules employed in either the FIG. 1 or FIG. 2 power transmissionshaving a directional module as indicated at 26 in FIG. 10. With such adirectional module where the direction of operation is determined byengagement of the respective collar gears 52 and 53, it is necessary toprovide a means for decoupling the transmission in order to bring allrotating members in the transmission to a full stop. With all of therotating members being stopped, a directional change may be effected inthe module 26. If such synchronization were not provided, the variousgears 26 would suffer very rapid wear and possible failure whenattempting to shift from neutral position to either forward or reverse.This problem arises particularly when a converter is employed as aninput for the power transmission because of the tendency for its fluidcoupling to continue driving the power transmission. It would beextremely difficult to disengage either the gears 52 or 53 unless thedriving torque is interrupted.

In order to interrupt drive torque through the power transmission forthis purpose, a piston 151 provides a movable reaction surface to theleft of the spring 141. With the piston 151 moved to the left asillustrated by the solid line position in FIG. 1 1, the spring 141 andaccordingly the brake drum 117 are also allowed to move leftwardly.Leftward movement of the reaction disc 119 is limited by interaction ofthe stop collar 148 with the clutch hub 112. Since extension of thespring 141 is limited, the brake drum 117 is allowed to movesufficiently to the left for disengagement of the reduction brake.

After a directional shift is completed, the piston 151 may be shiftedrightwardly, for example, by means of fluid pressure within a cavity 152from a source (not shown). Rightward motion of the piston 151 is limitedby a retaining ring 153 in a position illustrated by broken lines at151. With the piston 151 shifted to the right, the spring 141 is againconditioned to permit operation of the reduction brake 41 in the mannerdescribed above with reference to FIGS. 5 and 79.

It is believed obvious in view of the preceding disclosure, that variousmodifications are possible for the friction device, as well as the powertransmission within the scope of the present invention.

In summary relative to the friction device, in particular, it isresponsive to torque transmission or relative rotation of its componentparts, either in one direction of relative rotation but preferably inboth directions as illustrated in the above disclosure. The device isalso self-energizing or self engaging.

The device is also positively engaging in that it does not absorb energyupon engagement and disengagement as in a conventional disc clutch forexample. In other words, the present friction device experiencessubstantially static, rather than dynamic, engagement and disengagement.Accordingly, its friction discs may be made of material having a veryhigh coefficient of friction to prevent substantially any possibility ofslip. The friction discs could also be made of wear-resistant steel toinsure reliable operation over a long period of time.

The ability of the device to experience engagement upon initiation ofrelative rotation between its component parts, either in one or bothdirections of relative rotation, enables the device to be preciselyself-timing. This characteristic facilitates control of the device asexemplified by the common control apparatus for the direct driveclutches and reduction brakes in the power transmission described above.

The particular planetary gear set described above is limited in thespread of reduction ratios. Other types of planetary reduction ratiosare also contemplated by the present invention, with the self-energizingdevice being used to hold the reaction member to the case, and thedirect clutch being used to lock the planetary gear set.

An overdrive module could also be employed in such a transmission, andmay be similarly regulated by a selfenergizing device of the typedisclosed above.

Another arrangement using this shift principle could also employparallel axis shafts connected by different gear ratios. One gear ratiowould transmit power through the self-energizing device, and the otherratio through the modulated clutch. The largest reduction ratio, ineither an underdrive or an overdrive module would use theself-energizing device.

I claim:

1. A power transmission module providing both direct and reduction driveratios, comprising an input shaft,

an output shaft,

a planetary gear set having a sun gear, a ring gear and a plurality ofplanetary gears mounted upon a rotatable carrier and engaged with thesun gear and ring gear, the input shaft being coupled for rotation withthe ring gear and the output shaft being coupled for rotation with thecarrier, direct drive clutch having relatively rotatable frictioncomponents respectively coupled for rotation with different portions ofthe planetary gear set and being selectively operable to cause rotationof the ring gear together with the sun gear,

a-self-energizing reduction brake having a pair of relatively rotatablefriction components coupled respectively to the sun gear and a fixedmember of the power transmission module for operation independently ofthe direct drive clutch, the reduction brake including means responsiveto torque forces acting on the sun gear in either direction of rotationfor selectively initiating engagement of its friction components to lockthe sun gear against rotation, one of the friction components in thedirect drive clutch being fixed to one of the friction components in thereduction brake,

common control means operatively coupled with the direct drive clutchand the reduction brake for selectively engaging the direct drive clutchto cause rotation of the ring gear together with the carrier andsubstantially simultaneously conditioning the reduction brake for'operation in an overrunning mode to prevent it from engaging in responseto torque forces acting upon the sun gear.

2. A power transmission module providing both direct and reduction driveratios, comprising an input shaft,

an output shaft,

a planetary gear set having a sun gear, a ring gear and a plurality ofplanetary gears mounted upon a rotatable carrier and engaged with thesun gear and ring gear, the input shaft being coupled for rotation withthe ring gear and the output shaft being coupled for rotation with thecarrier, direct drive clutch having relatively rotatable frictioncomponents respectively coupled for rotation with different portions ofthe planetary gear set and being selectively operable to cause rotationof the ring gear together with the sun gear,

a self-energizing reduction brake having a pair of relatively rotatablefriction components coupled respectively to the sun gear and a fixedmember of the power transmission module, the reduction clutch includingmeans responsive to torque forces acting on the sun gear for selectivelyinitiating engagement of its friction components independently fromoperation of the direct drive clutch, to lock the sun gear againstrotation, one of the friction components in the direct drive clutchbeing fixed to one of the friction components in the reduction brake,and

common control means operatively coupled with the direct drive clutchand the reduction brake for selectively engaging the direct drive clutchto cause rotation of the ring gear together with the carrier andsubstantially simultaneously conditioning the reduction brake foroperation in an overrunning mode to prevent if from engaging in responseto torque forces acting upon the sun gear,

the common control means for simultaneously conditioning the reductionclutch and direct drive clutch comprising a separate actuating pistonoperatively coupled with each of the clutch and brake and a commonhydraulic passage for communicating actuating fluid against the pistons.

3. The power transmission module of claim 2 wherein the common fluidpassage is in communication with the direct drive clutch piston by meansof a restrictive orifice in order to modulate actuation of the directdrive clutch by its piston in relation to action upon the reductionbrake by its piston.

4. The power transmission module of claim 2 wherein the common controlmeans for selectively engaging the direct drive clutch and substantiallysimultaneously conditioning the reduction brake includes means forselectively delaying engagement of the direct drive clutch in order toprovide a modulating effect.

5. The power transmission module of claim 4 wherein the common controlmeans is a hydraulic control circuit having a common inlet passage, thedelaying means comprising a restrictive orifice for communicating thecommon passage with hydraulically responsive means operable for engagingthe direct drive clutch.

6. The power transmission module of claim 4 wherein the delaying meanscomprises mechanical spring means for operatively coupling the commoncontrol means with the direct drive clutch.

7. A power transmission comprising a plurality of sequential speed ratiomodules each providing both direct and reduction drive ratios, each ofthe modules comprising a fixed housing,

an input shaft, prime mover means being coupled to the input shaft of afirst sequential module,

an output shaft, the output shaft of the first sequential module beingcoupled with the input shaft of the next sequential module, the outputshaft of the last sequential module being coupled with a drive shaft,

a planetary gear set having a sun gear, a ring gear and a plurality ofplanetary gears mounted upon a rotatable carrier and engaged with thering gear and sun gear, the input shaft being coupled for rotation withthe ring gear and the output shaft being coupled for rotation with thecarrier,

a direct drive clutch being selectively operable to cause rotation ofthe ring gear together with the carrier,

a selfenergizing reduction brake functioning in response to torqueforces acting upon sun gear to selectively lock the sun gear againstrotation,

the reduction brake of each module including means responsive to torqueforces acting on the sun gear in either direction of rotation forselectively initiating engagement of its friction components to lock thesun gear against rotation, and

common control means for engaging the direct drive clutch to causerotation of the ring gear in common with the carrier and substantiallysimultaneously conditioning the reduction brake to prevent if from beingengaged, the common means also selectively functioning to disengage thedirect drive clutch and substantially simultaneously condition thereduction brake 'for selectively locking the sun gear against rotationin response to the torque forces acting thereon.

8. A power transmission comprising a plurality of sequential speed ratiomodules each providing both direct and reduction drive ratios, each ofthe modules comprising a fixed housing,

an input shaft, prime mover means being coupled to the input shaft of afirst sequential module,

an output shaft, the output shaft of the first sequential module beingcoupled with the input shaft of the next sequential module, the outputshaft of the last sequential module being coupled with a drive shaft,

a planetary gear set having a sun gear, a ring gear and a plurality ofplanetary gears mounted upon a rotatable carrier and engaged with thering gear and sun gear, the input shaft being coupled for rotation withthe ring gear and the output shaft being coupled for rotation with thecarrier,

a direct drive clutch being selectively operable to cause rotation ofthe ring gear together with the carrier,

a self-energizing reduction brake functioning in response to torqueforces acting upon the sun gear to selectively lock the sun gear againstrotation, the reduction brake being operable independent of the directdrive clutch, and

common control means for engaging the direct drive clutch to causerotation of the ring gear in common with the carrier and substantiallysimultaneously conditioning the reduction brake to prevent it from beingengaged, the common means also selectively functioning to disengage thedirect drive clutch and substantially simultaneously condition thereduction brake for selectively locking the sun gear against rotation inresponse to the torque forces acting thereon,

the common control means for simultaneously conditioning the reductionbrake and direct drive clutch of each module comprising a separateactuating piston operatively coupled with each of the clutches and acommon hydrualic passage communicating actuating fluid against thepistons.

9. The power transmission of claim 8 further comprising a torqueconverter input module, a directional control module including axiallymovable gear means for selectively establishing forward and reverseoperation and additional control means operatively coupled with thereduction brake of a speed ratio module preceding the directionalcontrol module in the power transmission for selectively conditioningthe reduction brake to prevent it from being engaged.

10. The power transmission of claim 8 wherein the common fluid passageis in communication with the direct drive clutch piston by means of arestrictive orifice in order to module actuation of the drive clutch byits control circuit having a common inlet passage, the delaying meanscomprising a restrictive orifice for communicating the common passagewith hydraulically responsive means operable for engaging the directdrive clutch.

13. The power transmission module of claim 11 wherein the delaying meanscomprises mechanical spring means for operatively coupling the commoncontrol means with the direct drive clutch.

1. A power transmission module providing both direct and reduction driveratios, comprising an input shaft, an output shaft, a planetary gear sethaving a sun gear, a ring gear and a plurality of planetary gearsmounted upon a rotatable carrier and engaged with the sun gear and ringgear, the input shaft being coupled for rotation with the ring gear andthe output shaft being coupled for rotation with the carrier, a directdrive clutch having relatively rotatable friction componentsrespectively coupled for rotation with different portions of theplanetary gear set and being selectively operable to cause rotation ofthe ring gear together with the sun gear, a self-energizing reductionbrake having a pair of relatively rotatable friction components coupledrespectively to the sun gear and a fixed member of the powertransmission module for operation independently of the direct driveclutch, the reduction brake including means responsive to torque forcesacting on the sun gear in either direction of rotation for selectivelyinitiating engagement of its friction components to lock the sun gearagainst rotation, one of the friction components in the direct driveclutch being fixed to one of the friction components in the reductionbrake, common control means operatively coupled with the direct driveclutch and the reduction brake for selectively engaging the direct driveclutch to cause rotation of the ring gear together with the carrier andsubstantially simultaneously conditioning the reduction brake foroperation in an overrunning mode to prevent it from engaging in responseto torque forces acting upon the sun gear.
 2. A power transmissionmodule providing both direct and reduction drive ratios, comprising aninput shaft, an output shaft, a planetary gear set having a sun gear, aring gear and a plurality of planetary gears mounted upon a rotatablecarrier and engaged with the sun gear and ring gear, the input shaftbeing coupled for rotation with the ring gear and the output shaft beingcoupled for rotation with the carrier, a direct drive clutch havingrelatively rotatable friction components respectively coupled forrotation with different portions of the planetary gear set and beingselectively operable to cause rotation of the ring gear together withthe sun gear, a self-energizing reduction brake having a pair ofrelatively rotatable friction components coupled respectively to the sungear and a fixed member of the power transmission module, the reductionclutch including means responsive to torque forces acting on the sungear for selectively initiating engagement of its friction componentsindependently from operation of the direct drive clutch, to lock the sungear against rotation, one of the friction components in the directdrive clutch being fixed to one of the friction components in thereduction brake, and common control means operatively coupled with thedirect drive clutch and the reduction brake for selectively engaging thedirect drive clutch to cause rotation of the ring gear together with thecarrier and substantially simultaneously conditioning the reductionbrake for operation in an overrunning mode to prevent if from engagingin response to torque forces acting upon the sun gear, the commoncontrol means for simultaneously conditioning the reduction clutch anddirect drive clutch comprising a separate actuating piston operativelycoupled with each of the clutch and brake and a common hydraulic passagefor communicating actuating fluid against the pistons.
 3. The powertransmission module of claim 2 wherein the common fluid passage is incommunication with the direct drive clutch piston by means of arestrictive orifice in order to modulate actuation of the direct driveclutch by its piston in relation to action upon the reduction brake byits piston.
 4. The power transmission module of claim 2 wherein thecommon control means for selectively engaging the direct drive clutchand substantially simultaneously conditioning the reduction brakeincludes means for selectively delaying engagement of the direct driveclutch in order to provide a modulating effect.
 5. The powertransmission module of claim 4 wherein the common control means is ahydraulic control circuit having a common inlet passage, the delayingmeans comprising a restrictive orifice for communicating the commonpassage with hydraulically responsive means operable for engaging thedirect drive clutch.
 6. The power transmission module of claim 4 whereinthe delaying means comprises mechanical spring means for operativelycoupling the common control means with the direct drive clutch.
 7. Apower transmission comprising a plurality of sequential speed ratiomodules each providing both direct and reduction drive ratios, each ofthe modules comprising a fixed hoUsing, an input shaft, prime movermeans being coupled to the input shaft of a first sequential module, anoutput shaft, the output shaft of the first sequential module beingcoupled with the input shaft of the next sequential module, the outputshaft of the last sequential module being coupled with a drive shaft, aplanetary gear set having a sun gear, a ring gear and a plurality ofplanetary gears mounted upon a rotatable carrier and engaged with thering gear and sun gear, the input shaft being coupled for rotation withthe ring gear and the output shaft being coupled for rotation with thecarrier, a direct drive clutch being selectively operable to causerotation of the ring gear together with the carrier, a self-energizingreduction brake functioning in response to torque forces acting upon sungear to selectively lock the sun gear against rotation, the reductionbrake of each module including means responsive to torque forces actingon the sun gear in either direction of rotation for selectivelyinitiating engagement of its friction components to lock the sun gearagainst rotation, and common control means for engaging the direct driveclutch to cause rotation of the ring gear in common with the carrier andsubstantially simultaneously conditioning the reduction brake to preventif from being engaged, the common means also selectively functioning todisengage the direct drive clutch and substantially simultaneouslycondition the reduction brake for selectively locking the sun gearagainst rotation in response to the torque forces acting thereon.
 8. Apower transmission comprising a plurality of sequential speed ratiomodules each providing both direct and reduction drive ratios, each ofthe modules comprising a fixed housing, an input shaft, prime movermeans being coupled to the input shaft of a first sequential module, anoutput shaft, the output shaft of the first sequential module beingcoupled with the input shaft of the next sequential module, the outputshaft of the last sequential module being coupled with a drive shaft, aplanetary gear set having a sun gear, a ring gear and a plurality ofplanetary gears mounted upon a rotatable carrier and engaged with thering gear and sun gear, the input shaft being coupled for rotation withthe ring gear and the output shaft being coupled for rotation with thecarrier, a direct drive clutch being selectively operable to causerotation of the ring gear together with the carrier, a self-energizingreduction brake functioning in response to torque forces acting upon thesun gear to selectively lock the sun gear against rotation, thereduction brake being operable independent of the direct drive clutch,and common control means for engaging the direct drive clutch to causerotation of the ring gear in common with the carrier and substantiallysimultaneously conditioning the reduction brake to prevent it from beingengaged, the common means also selectively functioning to disengage thedirect drive clutch and substantially simultaneously condition thereduction brake for selectively locking the sun gear against rotation inresponse to the torque forces acting thereon, the common control meansfor simultaneously conditioning the reduction brake and direct driveclutch of each module comprising a separate actuating piston operativelycoupled with each of the clutches and a common hydrualic passagecommunicating actuating fluid against the pistons.
 9. The powertransmission of claim 8 further comprising a torque converter inputmodule, a directional control module including axially movable gearmeans for selectively establishing forward and reverse operation andadditional control means operatively coupled with the reduction brake ofa speed ratio module preceding the directional control module in thepower transmission for selectively conditioning the reduction brake toprevent it from being engaged.
 10. The power transmission of claim 8wherein The common fluid passage is in communication with the directdrive clutch piston by means of a restrictive orifice in order to moduleactuation of the drive clutch by its piston in relation to acting uponthe reduction brake by its piston.
 11. The power transmission of claim 8wherein the common control means for selectively engaging the directdrive clutch and substantially simultaneously conditioning the reductionbrake of each module includes means for selectively delaying engagementof the direct drive clutch in order to provide a modulating effect. 12.The power transmission of claim 11 wherein the common control means ofeach module is a hydraulic control circuit having a common inletpassage, the delaying means comprising a restrictive orifice forcommunicating the common passage with hydraulically responsive meansoperable for engaging the direct drive clutch.
 13. The powertransmission module of claim 11 wherein the delaying means comprisesmechanical spring means for operatively coupling the common controlmeans with the direct drive clutch.